Catheters are routinely used in medicine for access to body spaces such as the urinary bladder, blood vessels, and portions of the biliary tree or abdominal or thoracic cavity. They are used mainly for monitoring, drainage and for infusion of fluids.
Especially where the insertion of a catheter involves piercing of other tissues, the Seldinger technique is frequently used for insertion. This involves gaining access to the body space with a hollow needle, advancement of a guidewire through the hollow part of the needle into the space, removal of the needle and then advancement of a catheter over the guidewire followed by removal of the guidewire. In other circumstances, such as the insertion of a urinary catheter through the urethra and into the bladder, catheters may be inserted without the use of a guidewire.
Any procedure involving cannulation of a body part entails the risk of infection. If aseptic technique is not adhered to, infection risks are greater. This is particularly so when placing central venous catheters, and is widely held to be true also for urinary catheters. Although sterile gloves are usually worn during insertion of catheters and guidewires, these can become contaminated. The operator may be unaware of this. A system, therefore, which does not involve touching objects which are inserted into the body would therefore be preferable.
Catheters and guidewires are elongated and in most cases their purpose mandates flexibility. This flexibility presents challenges for applying the necessary axial force for them to overcome the tissues' resistance to insertion and advancement without buckling of the catheter. The tendency to buckle can be mitigated by decreasing the distance between the point at which force is exerted on the catheter and the point at which resistance is encountered, by internal or external stiffeners or guides, or both. The needle through which a guidewire is inserted in the Seldinger technique serves as an external stiffener as well as to guide it to the correct place. Insertion of a urinary catheter requires repeated gripping of the catheter close to the urethral orifice, advancement by small distances and repeated repositioning of the grip.
A recent advance in the insertion of catheters and cannulas is the use of ultrasound for visualization of the relevant anatomy and to guide the insertion process. This involves the use of ultrasound gel on the skin at the site of insertion. This gel is slippery and makes the gripping and advancement of both guidewires and catheters prone to slippage and therefore more difficult. Gel may also be used as a lubricant for the insertion of a catheter, for example in the insertion of urinary catheters, with similar problems.
In the case of the insertion of central venous catheters, the common means for advancement of the guidewire involves pushing it with gloved digits along its path. For insertion of a urinary catheter, the urethral orifice is held steady and accessible with one hand whilst the lubricated catheter is fed into the orifice with the other. The procedure should not involve touching the catheter. It would ideally be pushed out of a perforated, sterile pouch which is split gradually along its length as the catheter is inserted. This is a difficult technique to master with one hand and even experienced health care practitioners frequently abandon the sterile pouch and feed the catheter manually.
In the case of insertion of a nasogastric tube (NGT) in an unconscious patient, the NGT is fed through one of the patient's nostrils into the nasopharynx and thence into the pharynx. At this point it is usually necessary to insert forceps through the patient's mouth into the pharynx in order to grip the NGT and advance it into the esophagus. Because of the limited space it is usually necessary to grip, advance and release the NGT many times. The NGT is frequently difficult to feed in this manner as it has a tendency to flex at points of resistance to advancement, then recoil to its original position when the grip is released.
For the insertion of both urinary and central venous catheters, a technique or device which obviates the need for manual handling of the catheter and/or guidewire would make the task easier, quicker and, in theory, reduce the risk of infection. For the insertion of NGT's, a device which could advance an NGT in the pharynx without allowing the NGT to recoil distally would be advantageous.
Intermittent urinary self-catheterization is performed by patients with poorly functioning bladders and/or urinary incontinence. In this procedure a patient inserts a catheter through their urethra to empty their bladder when it requires emptying. It causes fewer urinary infections than a long-term urinary catheter but some patients are unable to perform the procedure because of limited dexterity. A device which makes the procedure easier would allow more patients to self-catheterize and lower their likelihood of developing urinary infections.
Many catheters comprise, at their distal ends, drainage or infusion ports which are greater in diameter than the shafts of their respective catheters. In order to demount an advancement device from the catheter, it should either have sufficient internal diameter to allow for the size of said ports, or allow for demounting laterally so as to avoid said ports.